Phthalic acid (PA), Isophthalic acid (IP A), and Terephthalic acid (TP A) and their esters and derivatives are important precursors for the synthesis of polyesters and other useful materials.

The largest use of IP A and TP A at present is production of high performance polyamide and polyester polymers. For example, TPA is used to produce polyethylene terephthalate (PET) which is used extensively in consumer goods packaging, most prominently in the now ubiquitous clear plastic water bottles. IP A is also used to make polyesters as well as high performance polyamides. PA is an important precursor to plasticizers used in a range of polymers. Together PA, IP A, and TPA are produced on the scale of many millions of tons per year scale by oxidation of xylenes which are obtained from petroleum distillates.
There is strong demand from consumers and consumer goods companies for sustainable alternatives to petroleum-based plastics for packaging applications. Indeed, Coca Cola® and others have recently introduced PET containing biobased monoethylene glycol (MEG). Beverage bottles made from this PET are branded as the “Plant Bottle™” and have been well received in the marketplace. Unfortunately, since about 70% of the mass (and 8 out of every 10 carbon atoms) in PET derives from terephthalic and isophthalic acids, replacing petroleum-sourced MEG with biobased material yields PET that is only about 30% biobased. There is huge interest in biobased IP A and TPA to enable fully biobased PET production, but to date no economically feasible biobased processes exist.